We have a monovalent hapten-antibody complex which activates the first component of complement. We propose to use this complex to study the mechanism of activation of complement at the molecular level. We observe precipitation with bivalent haptens and bivalent antibody of high affinity. Precipitation in a bivalent system should not occur unless there exists an additional type of interaction. In this case, we have evidence that there exists protein-protein interactions between the antibody molecules. We propose to study and characterize these protein-protein interactions. Bruno Zimm has developed equations to predict the decrease in the sedimentation coefficient of very high molecular weight coil molecules in high centrifugal fields. We propose to test these equations experimentally for linear, double helical DNA. We will also study circular DNA for which no effect is predicted by Zimm's analysis. We will study the interaction between purified histones and histone complexes, and short, homogeneous, double helical, d(AT) oligonucleotides. We will study the distribution of VLDL lipoproteins in patients with lipid transport diseases using a computerized photoelectric scanning system with the ultracentrifuge, and also laser light scattering techniques. We plan to study the in vitro degradation of native and synthetic VLDL by lipoprotein lipase and lecithin cholesterol acyl transferase.